Neovascularization complicates a number of ocular conditions, and in the anterior segment of the eye often leads to a painful and destructive glaucoma. The factors controlling growth of new vessels are unknown. The ultrastructural morphology of the process has not been described in a comprehensive fashion. This study will seek further understanding of neovascularization of the iris by correlating observations made by scanning and transmission electron microscopy with the findings of iris angiography utilizing fluorescein and other tracer substances to reveal abnormalities of vascular permeability and growth. The study will be based on patients with iris neovascularization from any cause and on animals with experimentally induced growth of new vessels. The morphology of early proliferation is of special importance, since knowledge of this may suggest new therapeutic approaches to ocular neovascularization, which has become an increasingly common cause of blindness.